﻿<p>A generic and abstract relationship which subtypes are used to:</p>
<ul>
<li>assign a object type to an object occurrence</li>
<li>assign a property set to an object instance</li>
<li>assign a property set template to a property set</li>
</ul>

<blockquote class="example">
EXAMPLE&nbsp; Several instances of windows within
the IFC project model may be of the same (catalogue or
manufacturer) type. Thereby they share the same properties. This
relationship is established by the subtype
<em>IfcRelDefinesByType</em> of <em>IfcRelDefines</em> relationship
assigning an <em>IfcWindowStyle</em> to multiple occurrences
<em>IfcWindow</em>.
</blockquote>

<blockquote class="example">
EXAMPLE&nbsp; The (same) property set, e.g. 
Pset_ProductManufacturerInfo, keeping the manufacturer name,
label and production year of a product, can be assigned to one,
or many instances of furnishing. This relationship is established
by the subtype <em>IfcRelDefinesByProperties</em> of
<em>IfcRelDefines</em> relationship assigning an
<em>IfcPropertySet</em> to one or more instances of
<em>IfcFurnishingElement</em>.
</blockquote>

<blockquote class="history">
HISTORY&nbsp; New entity in IFC2x.
</blockquote>

<blockquote class="change-ifc2x4">
IFC4 CHANGE&nbsp; The attribute <em>RelatedObjects</em> had been demoted to the subtypes <em>IfcRelDefinesByProperties</em> and
<em>IfcRelDefinesByType</em>.
</blockquote>